Shielded wire covering



March 15, 1938. H THOMPSON 2,111,229

SHIELDED WIRE COVERING Filed June 2. 1934 Cbriciaafor" mav'fab/e 5/77676/ fil -1AM ATTORNEYJ Patented Mar. 15, 1938 UNITED STATE FFICE SHIELDED WIRE COVERING Application June 2, 11.934, Serial No. 728,80

3 (Claims.

This invention relates to improvements in electric conductors and particularly to the provision of a shielded covering adapted to substantially envelop a conductor.

The invention will be fully apparent from the following detailed disclosure when read in connection with the accompanying drawing and will be defined with particularity in the appended claims.

In the drawing- Fig. 1 is a view partly in section and partly in elevation of an electric conductor having a covering applied thereto embodying the invention; Fig. 2 is a view partly in section and partly in elevation of a, shielded tubing adapted to enclose an insulated conductor.

A characteristic feature of the invention relates to the provision of a jacket including interwoven strands of fibrous and metallic elements enveloped with a coating carrying metallic particles adapted to conductively coact with the metallic strands in order to form an efiective shielding envelope around the conductor. I deem it important to combine the metallic shielding strands of the sheath or coating surrounding the conductor with a layer of metallic shielding particles in order to secure an effective shield to cut down corona losses or to otherwise shield the enclosed conductor against electro-static disturbances.

The combined action of the coating of metallic particles and the metallic strands gives rise to more effective shielding than the presence of either the metallic particles alone or the metallic strands alone would give. It is believed that this superiority arises because the finely divided metallic particles used alone as a coating have a relatively low conductivity. And while the wires alone have a relatively high conductivity the interstices between adjacent wires provide gaps which I believe would cause current leakage due to the existence of corona. The metallic particles closing such gaps therefore conductively coact with the metallic strands with the result that an effective shielding envelope having a high overall conductivity about the conductor is secured, thus materially eliminating coronalosses.

The wire or conducting strands of the covering may constitute either part or all of the filling strands of a woven jacket whose warp strands are formed of cotton or other fibrous material. The presence of interwoven cotton strands with the wire is desirable because it lends flexibility to the covering and also provides a foundation to which the binder carrying the conductive metallic particles may readily adhere.

Referring to the accompanying drawing which exemplifies the invention, the cable, wire, or other conductor, is indicated at 118. This may be covered with any usual or suitable type of insulation indicated conventionally at l2. Over the insulation, there is secured a jacket indicated generally at M embodying the present invention. This jacket includes a multiplicity of longitudinally extending cotton or other fibrous warp strands it, which are interwoven with helical metallic filling strands l8. These strands are preferably of flexible wire, such as copper or the like of good conductivity. This wire may also be in the form of a flap strip or ribbon-like element.

I regard it important that the metallic helical member shall give a minimum of approximately seventy percent coverage in order to form an eifective shield. It is also desirable to form a conducting path between the adjacent convolutions of the metallic filling strands in order to negative the inductive characteristics which are inherently present in the helical current-carrying conductors. For this purpose, the outer layer of metallic particles indicated at 20 is provided and in some cases I also consider it important to include one or more warp strands l6 which will be formed of copper or other conducting material, such metallic warp strands can also be utilized for grounding the shielding cover. The powdery-like component of the shield may be carried in a suitable binder, such as cellulosic lacquer. Such lacquer is deemed advantageous because it resists attack by oil, water, gasoline, or the like. It also has a highdegree of flexibility. Thus the conductors embodying my invention are well suited for use as ignition cables or in other environments, where they are exposed to the normally deteriorating action of lubricating oil, gasoline, or the like. The binder, such as lacquer, can be adhesively bonded to the fibrous cotton strands, and thus the powdery metallic component-of the shield can be effectively and inseparably secured to the jacket formed of the interconnected metallic and fibrous strands.

Instead of securing the shield directly to the insulation of the covering, it is also contemplated that such shield may be furnished in the form of a tubing adapted to receive electric conductors, in which case the tubing of my invention will serve to shield the conductors housed therein. Fig. 2 illustrates such tubing wherein the fibrous warp strands are indicated at IS, the metallic parture from the invention as appended claims.

What I claim is:

1.In combination an electric conductor a shielded covering therefor comprising a jacket of interconnected copper and fibrous s'rands in which the copper strands constitute approximate- 13/ seventy percent of the superficial area of the jacket and a layer of metallic particles cone-um 'tively coacting with the copper strands to form a shielding envelope about the core, said metallic particles being interspersed throughout abinder characterized by flexibility and resistance to the destructive effect of water, oil and gasoline.

2. In combination with an electric conductor, a shielded covering therefor comprising a tu bular structure made up of longitudinalls extending fibrous warp strands and at least one longitudinally extending metallic warp strand, said warp strands being, interwoven with the convolutions of a helical metallic filling strand and layer of metallic particles interspersed throughout a body of cellulosic lacquer forming a flexibinder resistant to the deteriorating effects of oil, water and gasoline, the said metallic strands constit g not less than seventy perstructure i fective to negative the in- Wive cha acteristics which are inherently ent in said helical metallic strands.

3. In combination with an electrical conductor. covering therefor comprising: a tubular structure made up of longitudinally extending fibrous rp strands, said Warp strands being interwoven with the (101101Lltl01'15 of a flat ribbon-like helical metallic fil ng strand and a layer of metallic particles interspersed throughout a body of a flexible binder resistant to the deteriorating effects of oil, water and gasoline the said metallic strands constituting at least seventy percent of the supe; icial area of the shielded covering so as to negative the effect of currents which are normally set up by induction in such helical strands.

HARRY E. THOMPSON. 

